Acoustical panels (or tiles) are specifically designed systems that are intended to improve acoustics by absorbing sound and/or reducing sound transmission in an indoor space, such as a room, hallway, conference hall, or the like. Although there are numerous types of acoustical panels, a common variety of acoustical panel is generally composed of mineral wool fibers, fillers, colorants, and binders, as disclosed, for example, in U.S. Pat. No. 1,769,519, herein incorporated by reference in its entirety. These materials, in addition to a variety of others, can be employed to provide acoustical panels with desirable acoustical properties and other properties, such as color and appearance.
Fibrous panels, such as the base mats for traditional ceiling tiles and acoustical panels, are typically made using a wet forming process, as illustrated in FIG. 1. The components that will make up the fibrous panel are mixed in water to form a dispersion in a series of chests (or tanks) before being formed into the fibrous panel. In a conventional fibrous panel production method, the binder, cellulose, and mineral wool are first combined in a quick opening tank and mixed with water to form a pre-mixed slurry. The pre-mixed slurry is then transferred to a stock chest, where a mineral filler slurry is injected into the stock chest from a separate mixing device. An embodiment of such a mixing device, as referred to hereinafter, is a continuous mixer, sometimes referred to as a MARION MIXER. This mineral filler slurry is formed from a dry mineral filler powder mixed with water. Additional components or additives, such as flocculents or colorants, can also be added to the composition in the stock chest. The stock, comprising binder, cellulose, mineral filler, mineral wool, and any other additive is then transferred to a machine chest where it is held and mixed for a significant period of time to assure the mixture is homogeneous. After thorough mixing, the stock is introduced to a headbox of a forming machine and flowed on a moving, porous support wire screen, such as that of a Fourdrinier machine, to form a green board. The green board is then dewatered, first by gravity and then vacuum suction means, and subsequently dried in a heated convection drying oven or kiln to form the lightweight fibrous panel.
The wet forming process as described is well known in the art as the traditional platform to economically produce ceiling tiles with moderate acoustical performance. One deficiency of this process is the large amount to water required to manufacture these ceiling tiles. In this process, the bulk of the weight, approximately 70%, of the tiles prior to entering the kiln is water. This water is evaporated in the drying stage, but requires a significant amount of energy and resources to dry.